Wind turbines work by turning the kinetic energy of the wind into torque (a force) that causes the wind turbine to turn and drives an electrical generator. The wind is made up of real matter with mass, when mass is moving it has kinetic energy. As the wind causes the wind turbine to turn, we are reducing the energy in the wind. The energy that is removed from the wind is converted into mechanical energy that is used to drive an electrical generator and then converted into electrical energy.
The process of converting the wind into mechanical energy starts with the wind turbine blades. There are two different types of blade designs, lift type and drag type:
- Lift Type: This is a common type of the modern horizontal axis wind turbine blade that you see at all the big wind farms. This type of blade has a similar design of an airplane wing. As the air blows on both side of the blade, it takes the air long to travel across the leading edge creating a lower air pressure and higher air pressure on the tailing edge. This pressure difference ‘pulls’ and ‘pushes’ the blade around. Lift type blades have much higher rotational speeds than drag type, which make them well suited for generating electricity.
- Drag Type – The first type of wind turbines created used a drag design. This type of wind turbine uses the force of the wind to push the blade. A savonius is a perfect example of this design type, the wind is resisted by blade and the wind’s force on it pushes it around. This design normally creates a slower rotational speed with a higher torque than a lift type design. This design has been used for centuries for milling, sawing, pumping, but rarely used for energy generation on large scale.
The rotating blades are connected to a shaft which is connected to a generator. Some micro wind turbines are designed to be direct drive, where the blades connect directly to a low RPM generator, usually around 500+ RPM. The larger wind turbines make the use of gears to increase a slow blade turn, sometimes as slow as 9 RPM, into 1800+ RPM that can be used to drive a generator. These gears lose energy and cause additional cost, maintenance, and downtime. Many recent advances and ingenuity has gone into improving the design.
How is the electricity created?
The generator uses the turning motion to spin a magnetic rotor inside the generator housing that is surrounded by loops of copper wire (often wrapped around iron cores). As the rotor spins around the inside of the core it excites "electromagnetic induction" through the wire that generates an electrical current.
Where does the wind come from?
The sun’s energy fuels our wind. As solar rays come down hit Earth they heat it up. Wind is created by the Earth unevenly heating. The irregularities of the Earth cause the sun’s rays to heat differently from one area to the next. This creates areas with different pressures; nature will balance these differences by moving higher pressure air toward the lower pressure air which is wind.
Next: History of Wind Turbines